Method and apparatus for drying cellulose and like material in a continuous web



Dec. 7, 1937. v s. WELLMAR 2,101,301

METHOD AND APPARATUS FOR DRYING CELLULOSE AND LIKE MATERIAL IN A CONTINUOUS WEB Filed Aug. 9, 1933 2 Sheets-Sheet l Sven WeHmaY |NVENTO m ATT.Y.

Dec. 7, 1937. s WEL MAR 2,101,301

METHOD AND APPARATUS FOR DRYING CELLULOSE AND LIKE MATERIAL IN A CONTINUOUS WEB Filed Aug. 9, 1935 2 Sheets-Sheet 2 \{gven Wellmm [NVENTOK' 1 W 44 ATTY.

Patented Dec. 7, 1937 METHOD AND APPARATUS FOR DRYING CELLULOSE AND MATERIAL IN A CONTINUOUS WEB Sven Wellmar, Stockholm, Sweden Application August 9, 1933; Serial No. 684,294 In Sweden September 16, 1932 5 Claims.

The present invention relates to a method and apparatus for drying cellulose and like material in a continuous web without the web directly contacting or directly resting on the heat emitting surface as takes place for instance in cylinder drying machines.

According to the present invention the drying takes place in such a way that the web is intensively swept by warm air on both sides, at the same time as it is subjected to direct heat radiation, likewise on both sides, from heat surfaces disposed in the drying apparatus. Appa ratus for drying like material in a continuous web by means of warm air are known, but in the said apparatus the web is conveyed horizontally in a zigzag path through the drying apparatus by means of conveyors or the like.

According to the present invention the web is conveyed through the drying apparatus in a plurality of substantially vertical coils, i. e. in zigzag paths substantially in the vertical direction. In consequence hereof the web may be conveyed only by means of so called reverse cylinders without help of special conveying means.

This means is greatly simplified from a purely mechanical point of view, and moreover expensive space is spared. The heat surfaces, called heat elements in the following specification, are disposed between the coils, and are very effectively utilized by radiating heat from both sides thereof toward the material.

An embodiment of the invention is shown diagrammatically in the accompanying drawings in which Fig. 1 is a vertical longitudinal section, and.

Fig. 2 a vertical cross section of the apparatus.

Fig. 2a is a vertical section on line 2a-2a of Fig. 2 shown on a larger scale.

Fig. 3 shows a vertical longitudinal section through the apparatus, corresponding to Fig. 1, and

Fig. 4 shows a vertical cross section corresponding to Fig. 2.

Referring to the drawings, 1 denotes the walls or cover of the apparatus and 2 the upper reverse cylinders supporting the web. The lower reverse cylinders 3, the web' 4 to be dried and the heat radiating elements 5 may be of a known construction. 6 denotes the air distributing drums, through which the drying air is injected and distributed in the interior of the apparatus toward the web. According to the embodiment shown on the drawings, the said drums are provided with slots or apertures 1 on the underside and with an adjustable screen 8 by means of which the air currents obtain a discharge direction substantially perpendicularly to the web so as to rise along the web. By means of the said adjustable screen the intensity of the air currents may also be controlled at different points along the breadth of the web.

The position of the screen 8 relative to the corresponding slot 1 is controlled by means of screws 8a. Each screw engages a ribbon 8d fixed across the slot inside the drum. The screen is fastened between a shoulder 81) of the screw and a nut 80 on the screw 8a. After loosening the nuts 80 the screws can be turned for regulating the distance between the screen 8 and the slot 1. As the screen is comparatively thin one screw 80: may be turned more or less than another screw of the same screen and thus the screen may be brought in many different positions.

The drums by means of which the moist and cooled air is discharged from the apparatus are designated by 9 and 10. The said drums may also preferably be provided with screens or the like, in order to control the air current in the same way as the inlet drums.

The drying air is held in circulation by means of one or several fans H the air conduits l2 and I 3 of which are connected to the suction and pressure sides, respectively. In certain cases it may be preferable to provide heat elements also in the said conduits to preheat the air before it passes the elements 5 located in the drying apparatus itself.

In the embodiment shown on the drawings the invention is carried out in the following manner.

The moist web 4, which may consist of cellulose, cloth, or the like, is fed into the apparatus through an opening M in the wall I, and, as mentioned above, is conveyed in coils up and down around the reverse cylinders 2 and 3, and is discharged dry through the opening I5. The drying air, which is held at a suitable temperature, flows in at the bottom through the air distributing drums 6 and passes upward between the web 4 and the heat elements 5. Thus as the ascending air currents absorb the moisture they also absorb heat from the heat elements, thus increasing their capacity of absorbing further the moisture. At the same time the web is subjected to direct heat radiation from the elements 5.

The reverse cylinders are preferably made with a relatively small diameter, the drying apparatus thus obtaining a very small volume relatively to its capacity. In drying cellulose it has been found, due to the repeated bends in the two directions around the said reverse cylinders with a relatively small diameter, the cellulose becomes loosened and softened so that the surface becomes more porous. This is very important because the ,drying is facilitated by the moisture more easily when issuing from the interior layer of the web, the quality of the latter being improved. The web does not here contact conveying means or other metallic parts which only contact at times, and are cooled by the drying material, and which in the intervals are subjected to the action of warm air and heat radiation, and whereby they obtain a considerable overtemperature relatively to the material to be dried.

The reverse cylinders, which are partly subjected to heat radiation, obtain here a relatively low temperature due to the fact that they are I permanently cooled by the web the temperature of which is low on account of the water vaporization.

It will be understood from the foregoing that because of the way in which the dryingis carried out in this apparatus the highest possible efliciency is obtained, and since there are no lost spaces the drying apparatus obtains the least possible volume.

The heated drying air being allowed to pass along the web from the bottom to the top its natural rising force is also utilized to a certain extent. This does not, however, exclude the possibility of driving the drying air in the opposite direction.

In the embodiment illustrated in the drawings the fan (or the fans) for circulating theirir is placed outside the drying apparatus itself. This is, however, practically a matter of convenience since the fan (or the fansleln these embodiments of course may be placed within the drying apparatus itself.

The apparatus offers various possibilities of exchanging part of the drying air as ventilating air for removing the moisture. The fresh air may for instance be supplied to the circulation air through a damper or the like ii at the suction side of the fan II, whereas the corresponding moist quantity of air is removed in another way at the top of the apparatus where the moisture of the air is the greatest. The moist air may also be removed at the damper H at the pressure side of the fan, and the corresponding quantity of fresh air may be supplied to the interior of the apparatus at, another suitable place and in an-- other suitable manner.

The movement .of the web through the drying apparatus during the continuousfrlrying may take place in various ways according. to the kind of material to be dried. If it is the question of a relatively moist and loose cellulose web it might be necessary to have the outer drive coupled to most, or to all of the upper reverse cylinders 2 and possibly to the lower ones. But it might also be sufficient to carry the outgoing dried web between a pair of drawing cylinders so that the web is allowed to rotate all the reverse cylinders. Thus the said cylinders are coupled to their driving means so that they may be easily disconnected from the same.

When the web at the start is to be carried through the drying apparatus (so called point drawing) the manual work involved may be considerably reduced if the drying apparatus is provided with a device for automatic point drawing. Figs. 3 and 4 show a device for this purpose particularly adapted for this drying apparatus.

, tion.

The walls of the drying apparatus are also here indicated by I, the reverse cylinders by 2 and 3 respectively, and the web by 4.

Parallel with the web, but outside its borders two endless pliable bands, chains, ropes, such as steel wire, or the like run through the whole apparatus. The. said bands are indicated by dotted lines 2|, and run within the drying apparatus around special rope wheels or the like 22 and 23 which preferably may be loose on the shafts of the reverse cylinders 2 and 3 respectively.

Outside the drying apparatus itself the ropes run over discs 24 and 26 arranged in a suitable way, one or several pairs of which may be slldably mounted for stretching the ropes, and one pair of which must be provided with such a driving device allowing the two ropes to run synchronously through the drying apparatus. On the drawings for example the rope pairs 25 are driven by the belt pulleys 26. Between the ropes there is provided a rod or the like 21 which is divided or embodied in a suitable way so that the web may be readily fastened to the same. In Fig. 3 the rod 21 is shown in such a position that the web 4a may be fastened to the same. When the rope discs 25 are being started the point of the web is conveyed through the apparatus by means of the rod, and may be received and liberated at its outlet end.

The ropes 2| should preferably have a driving device independent from the reverse cylinders 2 and 3.

Some other details may be arranged in another suitable manner within the scope of this inven- As to the driving device itself the described apparatus is particularly flt for drying a continuously driven web, but it may also be employed in such cases in which it may be suitable with a gradual feeding of the web, for instance so that a part of the web corresponding to the capacity of. the apparatus is each time fed into, and discharged from the apparatus respectively.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. The herein described method of drying a continuous web of cellulose, cloth and the like in a chamber, which method consists in conveying the web through the chamber substantially continuously in a zig-zag path and in generally vertical coils with the web hanging between the points of reversal, forcing warm air into the spaces between the vertical runs of the web by means of inlet ducts extending into the space between each of two consecutive vertical runs of the web, respectively, adjacent one of the points of reversal and projecting substantially across the width of the web, distributing the air from said duct and blowing it against the web at points disposed substantially over the full width thereof, discharging the air adjacent the other point of reversal at points disposed over substantially the full width of the web, and supplying radiant heat to said compartment, whereby both sides of the web are subjected simultaneously to radiant heat and to the warm air.

2. A drying apparatus for a continuous web of cellulose, cloth and the like, comprising a drying chamber, a group of upper and a group of lower reverse cylinders in said chamber for the conveyance of the web in an almost vertical zigzag path over said cylinders, heat radiating elements in the spaces between the vertical runs of the web, means forcontrolling the circulation of the air through the drying chamber, comprising groups of air ducts' disposed within the spaces between each of two consecutive vertical runs of the web, one group of ducts being air distributing ducts, each thereof being disposed adjacent one end of each of the spaces between two consecutive runs of the web, and the other group of ducts constituting the discharge ducts,

the latter being disposed adjacent the opposite,

cellulose, cloth and the like, comprising a drying chamber, a group of upper and a group of lower reverse cylinders in said chamber for the conveyance of the web almost vertically in a zig-zag path over said cylinders, heating elements in the spaces between the vertical runs of the web, means for controlling the circulation of the air through the drying chamber comprising a warm air supplying main duct, a number of air distributing branch ducts, at least one for each space between two consecutive vertical runs of the web, mounted alternately above and above and adjacent to the lower reverse cylinders, a main air discharging duct uniting a number of air discharging branch ducts mounted below the upper reverse cylinders, all branch ducts extending substantially over the full width of the path of the web.

4. A drying apparatus for a continuous web of cellulose, cloth and the like, comprising a drying chamber, a group of upper and a group of lower reverse cylinders in said chamber for the conveyance of the web almost vertically in a zigzag path over said cylinders, heat radiating elements in the spaces between the vertical runs o! the web, means for controlling the circulation of the airthrough the drying chamber comprising groups of air ducts mounted within said spaces between the vertical runs of the web adjacent the vertical ends thereof, one group of ducts being air distributing ducts and the other group of ducts, mounted opposite said one, being air discharging ducts, the air distributing ducts extending across the path of the web substantially over the full width thereof within the spaces between each of two consecutive vertical runs of the web said air distributing ducts having longitudinal discharge slots therein and adjustable deflectors before said slots to direct the flow of warm air against the flat sidesoi the web.

5. A drying apparatus for a continuous web of cellulose cloth and the like, comprising a drying chamber, a group of upper and a group of lower reverse cylinders in said chamber for the conveyance of the web almost vertically in a zigzag path over said cylinders, heating elements on both sides of the path ofv the web and vertically above the lower and below the upper reverse cylinders, means tor forcing ventilating drying air into the spaces between the vertical runs of the web, comprising groups oi! air ducts mounted substantially parallel with the reverse cylinders and projecting at the top and at the bottom into the spaces between each of two consecutive vertical runs of the web, said air supply and air discharging ducts and an air circulation conduit constituting a closed circulation system except for their outlets for moist air and inlets for fresh'air, said air distributing and air discharging ducts having longitudinal slots facing the spaces between the vertical runs of the web and adjustable deflectors mounted on the discharge side of the inlet ducts to control the intensity oi the air currents in a lateral direction with respect to the web. SVEN WELLMAR. 

